Longbottom, 28, who is Australian by birth but eligible to play for England, has produced a series of outstanding performances in the current Super XV season.

Mark McCall, Saracens' director of rugby, said: "We are delighted that Kieran and Brigitta have decided to come to London. He has shown up consistently well in our scouting reports, and he will prove an outstanding addition to the squad."

"Saracens are recognised as one of the go-forward clubs in Europe," Longbottom said. "I'm really looking forward to this opportunity."